roll: third_party/pigweed pw_multibuf: Unify unit tests

This CL validates that the v1_adapter behaves the same as both the v1
and v2 versions of multibuf by applying the same v1 and v2 unit tests
to it.

NO_IFTTT=Android.bp's pw_sync dep is already correct.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/370521
Original-Revision: 992c1acc0167eda33eaf7941162f67cd6f68425a

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: f5da5b2d791635..992c1acc0167ed
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8688137598002206193
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id4a42f051ad2a9dfd31b6aced48900e59eb3d721
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/382378

third_party/pigweed

diff --git a/third_party/pigweed b/third_party/pigweed
index f5da5b2..992c1ac 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f5da5b2d79163561c7b3cb80e1228cecf98fbce5
+Subproject commit 992c1acc0167eda33eaf7941162f67cd6f68425a